1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device formed by stacking a plurality of semiconductor elements on a substrate.
2. Description of the Related Art
In a conventional method for manufacturing a semiconductor device, one semiconductor element is bonded face-down to electrodes provided on a carrier by means of its protruding electrodes. The carrier is tilted about 15° from the horizontal and a thermosetting liquid resin is injected into spaces between the carrier and the semiconductor element, which are defined by electrode bonding. Thereafter, the liquid resin is cured to seal the spaces defined by the electrode bonding, refer to, for example, Japanese Patent Application Laid-Open No. Hei 11 (1999)-354552, paragraphs 0022-0024 in the third page and FIG. 2.
It has recently been practice to stack a plurality of semiconductor elements on a substrate, electrically bond them to one another, and bring a semiconductor device into a large size and high functioning at low cost.
However, when an attempt to seal a plurality of spaces defined by stacking a plurality of semiconductor elements is made using the above prior art, electrodes of the lowest-stage semiconductor element are bonded to a substrate and a liquid resin is injected into the spaces and then cured. Thereafter, electrodes of the next-stage semiconductor element are bonded onto the lowest-stage semiconductor element, and the liquid resin is injected into spaces defined between the two semiconductor elements and cured. This is repeated in turn to fabricate a semiconductor device.
A problem arises in that, according to such a manufacturing method, after the liquid resin extruded from each space has been cured, the liquid resin extruded from the next space is superimposed thereon and cured, and when an interface is formed between these layers and peeling occurs in the interface, corrosion of electrodes or the like occurs due to moisture absorption from the peeled interface.
Also a problem arises in that moisture that remains at the peeled interface expands due to heating in a reflow process at secondary mounting of the semiconductor device, thereby causing breakage of a junction between the electrodes.
Further, a problem arises in that since the peeled interface has no bonding force, stress due to the difference in thermal expansion between a metal material and the cured liquid resin from heat generated by the semiconductor device occurs in the junction between the electrodes, thus causing breakage of the junction between the electrodes due to thermal cycles.
Furthermore, a problem arises in that since the liquid resin extruded from each space is cured and the liquid resin is superimposed thereon in turn to seal the spaces among the semiconductor elements or the like, the extruded liquid resin expands over the substrate in turn and a relatively large area for placing the extruded liquid resin is needed, thus making it difficult to bring a semiconductor device into lesser size.
A problem arises in that when one attempts to inject the liquid resin into the plural spaces one at a time in order to cope with such a problem, it is difficult to uniformly inject the liquid resin into the respective spaces even though the carrier is tilted about 15° from the horizontal, and a sealing failure occurs in each space in which the amount of injected the liquid resin is insufficient.
The present invention has been made to solve the foregoing problems. It is therefore an object of the present invention to provide a means which is capable of uniformly injecting a liquid resin into spaces such as spaces among a plurality of semiconductor elements, which are formed by stacking the plurality of semiconductor elements, and which prevents the formation of an interface between layers each formed by the post-curing liquid resin.